NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

VERSIONS

ATTRIBUTES

CONFORMING TO

NOTES

SEE ALSO

COLOPHON

## NAME

## SYNOPSIS

## DESCRIPTION

## RETURN VALUE

## ERRORS

## VERSIONS

## ATTRIBUTES

## CONFORMING TO

## NOTES

## SEE ALSO

## COLOPHON

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

VERSIONS

ATTRIBUTES

CONFORMING TO

NOTES

SEE ALSO

COLOPHON

round, roundf, roundl − round to nearest integer, away from zero

**#include
<math.h>**

**double
round(double** *x***);
float roundf(float**

long double roundl(long double

Link with
*−lm*.

Feature Test
Macro Requirements for glibc (see
**feature_test_macros**(7)):

**round**(),
**roundf**(), **roundl**():

_XOPEN_SOURCE >= 600
|| _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;

or *cc -std=c99*

These functions
round *x* to the nearest integer, but round halfway
cases away from zero (regardless of the current rounding
direction, see **fenv**(3)), instead of to the nearest
even integer like **rint**(3).

For example,
*round(0.5)* is 1.0, and *round(−0.5)* is
−1.0.

These functions return the rounded integer value.

If *x* is
integral, +0, −0, NaN, or infinite, *x* itself is
returned.

No errors occur. POSIX.1-2001 documents a range error for overflows, but see NOTES.

These functions first appeared in glibc in version 2.1.

For an
explanation of the terms used in this section, see
**attributes**(7).

C99, POSIX.1-2001, POSIX.1-2008.

POSIX.1-2001
contains text about overflow (which might set *errno*
to **ERANGE**, or raise an **FE_OVERFLOW** exception).
In practice, the result cannot overflow on any current
machine, so this error-handling stuff is just nonsense.
(More precisely, overflow can happen only when the maximum
value of the exponent is smaller than the number of mantissa
bits. For the IEEE-754 standard 32-bit and 64-bit
floating-point numbers the maximum value of the exponent is
128 (respectively, 1024), and the number of mantissa bits is
24 (respectively, 53).)

If you want to
store the rounded value in an integer type, you probably
want to use one of the functions described in
**lround**(3) instead.

**ceil**(3),
**floor**(3), **lround**(3), **nearbyint**(3),
**rint**(3), **trunc**(3)

This page is
part of release 4.04 of the Linux *man-pages* project.
A description of the project, information about reporting
bugs, and the latest version of this page, can be found at
http://www.kernel.org/doc/man−pages/.